Virtually all semiconductor fabrication facilities include one or more clean rooms in which the total number of particles per unit volume is tightly controlled along with the temperature and the humidity. For example, a Class 100 clean room has a dust count of no more than 100 particles having diameters of 0.5 .mu.m or larger per cubic foot. As known to those skilled in the art, semiconductor fabrication processes are performed in a clean room since airborne particles can settle on semiconductor wafers and/or lithographic masks and cause defects in the resulting semiconductor wafer or device. For example, a particle on a semiconductor surface can disrupt the single crystal growth of an epitaxial layer and can disadvantageously cause the formation of dislocations.
While significant measures are taken to limit the number of particles which enter a clean room, such as by requiring clean room personnel to wear various lab coats, hats, masks and/or bunny suits, the equipment, including the furniture, within a clean room unfortunately also tends to emit a number of particles. For example, chairs used in clean rooms oftentimes emit particles when clean room personnel alternately sit down and stand up.
Typically, the chairs that are used in clean rooms include a seat, a back rest, a base and, in some instances, arm rests. While the base could be formed by three or four legs, the base of the chairs typically utilized in clean rooms generally include a telescoping pedestal for supporting the seat and for adjusting the height of the chair. In addition, the base of the typical chair used in a clean room includes a number of arms which extend radially outward from the lower end of the pedestal as well as a number of wheels, castors or rollers on the end portions of respective ones of the radially extending arms. As such, clean room personnel can move, i.e., roll, about the clean room while seated in the chair.
Typically, the seat and the back rest of the chairs conventionally used in clean rooms are formed of vinyl or a hard, compressed rubber material. As a result of the alternate compression and expansion of the seat member and the back rest as clean room personnel sit down in the chair and stand up from the chair, respectively, the seat and the back rest generally emit particles into the clean room atmosphere. In addition, the telescopic height adjustment of the chair provided by the pedestal also generates a number of particles that are emitted into the clean room atmosphere. As with other particles that enter the clean room atmosphere, a certain percentage of the particles will eventually settle on the semiconductor wafer or the lithographic mask so as to create defects in the resulting semiconductor wafer or device.